Caffeine

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

No data are available.

Additional information

In a Two-generation reproduction study (Reproductive Assessment by Continuous Breeding Study) (NTP, 1984 a and b), Caffeine (purity >98.5%) was administered to CD-1 mice in water at dose levels of 0, 120, 250, or 500 ppm (0, 22, 44, or 88 mg/kg bw/day). The study was conducted simultaneously by two independent laboratories; one laboratory conducting Tasks 1, 2 , and 3; the other laboratory conducting the Tasks 1, 2, and 4, respectively.

The first laboratory (Tasks 1, 2, and 3) reported that treated mice lost facial hair, but the percentages and groups involved were not specified. There was no effect on the mean number of litters/pair produced, or on the aggregate mean number of pups/litter. There was a 20% reduction in live male pups/litter, however. Evaluating each litter individually, after the first litter, the high dose group always delivered 1-2 pups less than the controls; at the fifth litter, the controls delivered a mean of 10.3 ± 7 pups (mean ± SEM), while the high dose group delivered a mean of 8.6 ± 1 pups. The proportion of pups born alive was reduced by 3%, 5%, and 5% in the low, middle and high dose groups, respectively. Additionally, pup body weight adjusted for litter size was reduced by 4% at the high dose. Female body weight at necropsy was reduced by 5%, while body-weight-adjusted organ weights were unchanged. Ante-mortem vaginal cyclicity was unaffected by caffeine exposure. Male body weight was unchanged by consumption of 0.05% caffeine, but adjusted liver weight was increased by 10%. Absolute testis weight dropped by 7% and adjusted seminal vesicles weight decreased by 12%. Sperm motility values for controls was low (47% motile), so the 21% reduction in the treated group should be viewed with caution. Similarly, the control epididymal sperm density was nearly equal to half of the subsequent control values for this lab, so the significant increase in sperm density in the caffeine-treated group is likely erroneous.

A crossover mating trial (Task 3) was performed. There were no differences between the groups in the mating and fertility indices, and no differences with respect to pup number or viability or weight.

The slight but significant reductions in (male) pup number, pup viability, and adjusted pup weight suggest that caffeine produced some slight reproductive toxicity. This occurred in the presence of very slight indications of other toxicities (body or organ weight changes).

The second laboratory (Tasks 1, 2, and 4) reported that there were no effects on body weight of the parental animals. Alopecia occurred in 55% of the medium dose and 50% of the high dose animals. While there were no exposure-related changes in the number of litters/pair, viability, or adjusted pup weight, the number of live pups per litter, averaged over the 4-5 litters, dropped 15% at the medium dose and 20% for the high dose animals. No crossover mating trial was conducted, and the offspring from the last litter of control and high dose mice were reared by their dams until weaning, when they were given the same treatment as their parents until mating at 74 ± 10 days of age.

At the second generation mating trial, there were no changes in any reproductive endpoint.

At necropsy, at 0.05% caffeine, male body weight was reduced by 8% while male adjusted liver weight increased by 8%. No change was found in female body or organ weights, or in any sperm endpoint.

In conclusion, a reduction in the number of live pups/litter for the F0 generation was the only reproductive effect observed in this study. This occurred in the absence of a change in body weights in the F0 parental mice.

The NOAEL is 120 ppm (22 mg/kg bw/day) for both parental (P) and offspring (F1) and 500 ppm (88 mg/kg bw/day) for the F2 mice.

This study is acceptable and satisfies the guideline requirement for a Two-generation reproductive study (OPPTS 870.3800; OECD 416) in mice.

In another Two-generation reproduction study (Reproductive Assessment by Continuous Breeding Study) (NTP, 1996), Caffeine (purity 98.6%) was administered to Sprague-Dawley rats by gavage at dose levels of 0, 12.5, 25, or 50 mg/kg bw/day. During Task 1 (i.e. range-finding study), groups of 45 males and 45 females were used; during Task 2, groups of 90 males and 90 females were used; during Task 3, 50 naive males and 50 naive females were used in addition to Task 2 animals; during Task 4, 2 males and 2 females from each litter were used.

During Task 2, live pup weight adjusted for litter size was decreased by 7, 7, and 8% in the 12.5, 25, and 50 mg/kg dose groups, respectively. No differences were observed in other reproductive endpoints. The decreased pup weight was observed concomitant with reduced dam weight gain. Throughout the study, the body weights were less than controls in the F0 rats at any dose level. Mean feed consumption was transiently decreased in the 25 and 50 mg/kg animals. At necropsy, no differences were noted in F0 male or female absolute organ weight data; however, many relative organ weights (mg/g body weight) were increased in all dosed groups when compared to controls. These differences were attributed to the decrease in terminal body weights. No treatment-related gross or microscopic lesions were observed in the F0 animals.

Evaluation of F0 computer-assisted sperm analysis (CASA) data revealed a treatment-related decrease in percent motile sperm in the 50 mg/kg F0 males compared to controls. The sperm velocity was decreased in all treated males. The average radius was also decreased in all treated males. The percent normal sperm was decreased slightly in the 50 mg/kg males when compared to controls. The remaining sperm endpoints were comparable among all groups.

The crossover mating trial (Task 3) revealed no changes on male or female fertility or in pup weight. Reproductive parameters were comparable between dose groups when naive males were mated with control or 50 mg/kg females and when naive females were mated with control or 50 mg/kg males.

In Task 4 (second generation evaluation), no treatment-related differences were observed in pup weights during lactation. From the initiation of dosing (PND 22) through the maturation phase up to the termination of Task 4, mean body weights of the F1 low-to-high dose males and females were decreased when compared to controls. Mean feed consumption values were decreased in all treated groups during Task 4. No mortality was observed in any of the F1 animals.

Measures of reproductive performance of second generation breeding pairs revealed a decrease in the number of live F2 pups per litter and proportion of pups born alive in the 50 mg/kg dose group. No differences were observed between dose groups in other endpoints.

At necropsy, many decreases were noted in F1 absolute organ weight data and many increases in F1 relative organ weights were observed in all treated groups when compared to controls. These differences may be attributed to the decreased terminal body weights. No treatment-related gross or microscopic lesions were observed in the F1 animals.

As observed in the F0 males, a decrease in percent motile sperm and sperm velocity was observed in the 50 mg/kg F1 males compared to controls. The average radius was also decreased in the 25 and 50 mg/kg groups. The remaining sperm parameters were unchanged.

The no-observable-adverse-effect level (NOAEL) was not established in this study as the 12.5 mg/kg animals displayed reduced body weight gain.

This study is acceptable and satisfies the guideline requirement for a Two-generation reproductive study (OPPTS 870.3800; OECD 416 in rats.

HUMAN DATA:

Effects on reproduction

Christian and Brent, 2001 concluded in their recent review on reproductive and developmental risks of caffeine that the usual range of human exposures to caffeine from food and beverages is below the threshold dose that would result in developmental/teratogenic or reproductive effects.

With regard to the endpoints low birth weight and spontaneous abortion, some studies of good quality and power have suggested an increased risk with higher coffee consumption (mostly more than 300 mg/day). Therefore, these endpoints will be addressed more in detail while the evidence of other adverse effects can be considered as inadequate based on the presently available data.

 

Delayed conception and infertility

Delayed conception was reported in association with coffee consumption of four to seven cups/day or caffeine consumption as little as 100 mg/day (total dose)(Christianson et al., 1989, Wilcox et al., 1988, Williams et al., 1990, Hatch and Bracken, 1993, Stanton and Gray, 1995, Bolumar et al., 1997, Curtis et al., 1997).These findings were not confirmed in other studies(Riduan Joesoef et al., 1990, Hakim et al., 1998, Jensen et al., 1998)or a slight association was only seen in women who smoked and also consumed at least 8 cups of coffee per day(Olsen, 1991). Lack of information on confounder like female body mass index, hormonal status, disease of female reproductive organs, semen quality, frequency of intercourse, especially in the studies reporting delayed conception, suggests that these findings need further verification.

Risk of infertility due to tubal disease or endometriosis was observed in women consuming upper levels of caffeinated beverages (more than 7 g/month) (Grodstein et al., 1993). No significant association between consumption of caffeinated beverages, except tea, and infertility was found in a prospective study(Caan et al., 1998).

Effects on sperms

The addition of caffeine to human sperm increased sperm motility(IARC 1991). In a cross-sectional study in male volunteers aged 19-35 common lifestyle factors (smoking, caffeine, and alcohol) were associated with increased frequencies of sperm aneuploidy (Robbins et al. 1997). No significant effects of smoking, caffeine intake, and alcohol consumption on sperm morphometric parameters were observed in another cross-sectional study in male volunteers aged 18-35(Vine et al. 1997).Conclusion: Data are inadequate for an assessment.

Short description of key information:
In a Two-generation reproduction study (Reproductive Assessment by Continuous Breeding Study) (NTP, 1984 a and b), Caffeine (purity >98.5%) was administered to CD-1 mice in water at dose levels of 0, 120, 250, or 500 ppm (0, 22, 44, or 88 mg/kg bw/day). A reduction in the number of live pups/litter for the F0 generation was the only reproductive effect observed in this study. This occurred in the absence of a change in body weights in the F0 parental mice.
The NOAEL is 120 ppm (22 mg/kg bw/day) for both parental (P) and offspring (F1) and 500 ppm (88 mg/kg bw/day) for the F2 mice.

In another Two-generation reproduction study (Reproductive Assessment by Continuous Breeding Study) (NTP, 1996), Caffeine (purity 98.6%) was administered to Sprague-Dawley rats by gavage at dose levels of 0, 12.5, 25, or 50 mg/kg bw/day.
The no-observable-adverse-effect level (NOAEL) was not established in this study as the 12.5 mg/kg animals displayed reduced body weight gain.

HUMAN DATA
The usual range of human exposures to caffeine from food and beverages is below the threshold dose that would result in developmental/teratogenic or reproductive effects (Christian and Brent, 2001) .

Effects on developmental toxicity

Description of key information

In a developmental toxicity study (NTP, 1984), Caffeine (purity not given) was administered to 20 CD rats/dose by gavage at dose levels of 0, 40, or 80 mg/kg bw/day from days 1 through 19 of gestation. 
The maternal LOAEL is 40 mg/kg bw/day (the lowest dose administered), based on reduced weight gain. The maternal NOAEL <40 mg/kg bw/day. 
The overall developmental LOAEL is 40 mg/kg bw/day, based on decreased fetal weight. The developmental NOAEL (embryo-/fetotoxicity) is 40 mg/kg bw/day, based on decreased fetal weight observed at 80 mg/kg bw/day. The developmental NOAEL (teratogenicity) is > 80 mg/kg bw/day. 
In another part of the same study (NTP, 1984), which was designed to evaluate the postnatal development and function after oral caffeine exposure, Caffeine (purity not given) was administered to 12 CD rats/dose by gavage at doses of 0, 10, 20 or 40 mg/kg from days 1 through 20 of gestation. Dams were allowed to deliver, and the pups were subsequently evaluated for postnatal growth and several functional parameters: swimming, developmental activity, blood pressure and electrocardiographic recordings. 
The maternal LOAEL is 10 mg/kg bw/day, based on reduced weight gain. The maternal NOAEL is <10 mg/kg bw/day. 
The developmental NOAEL is >40 mg/kg bw/day, the highest dose administered. 
In a further developmental toxicity study (Collins et al., 1983), Caffeine (purity >=98.5%) was administered to 61 Osborne-Mendel rats/dose in water at dose levels of 0, 70, 180, 360, 700, 1000, 1500, or 2000 ppm from days 0 through 20 of gestation. 
The maternal NOAEL is ca. 50.7 mg/kg bw/day. (360 ppm in the drinking water). 
The developmental NOAEL (embryo-/fetotoxicity ca. 10.1 mg/kg bw/day (70 ppm in the drinking water), based on delayed ossification. 
The developmental NOAEL (teratogenicity) is >204.5 mg/kg bw/day (2000 ppm in the drinking water, the highest dose administered). 
In a battery of developmental toxicity investigations (Gilbert and colleagues, 1988-1994) C...

Additional information

In a developmental toxicity study (NTP, 1984), Caffeine (purity not given) was administered to 20 CD rats/dose by gavage at dose levels of 0, 40, or 80 mg/kg bw/day from days 1 through 19 of gestation.

Doses of 40 and 80 mg/kg caffeine significantly reduced maternal weight gain during pregnancy, but did not increase the prenatal death or malformation rate. Fetal weight was significantly reduced by the 80 mg/kg dose.

The maternal LOAEL is 40 mg/kg bw/day (the lowest dose administered), based on reduced weight gain. The maternal NOAEL is < 40 mg/kg bw/day.

The overall developmental LOAEL is 40 mg/kg bw/day, based on decreased fetal weight. The developmental NOAEL (embryo-/fetotoxicity) is 40 mg/kg bw/day, based on decreased fetal weight observed at 80 mg/kg bw/day. The developmental NOAEL (teratogenicity) is > 80 mg/kg bw/day.

In another part of the same study (NTP 1984), which was designed to evaluate the postnatal development and function after oral caffeine exposure, Caffeine (purity not given) was administered to 12 CD rats/dose by gavage at doses of 0, 10, 20 or 40 mg/kg from days 1 through 20 of gestation. Dams were allowed to deliver, and the pups were subsequently evaluated for postnatal growth and several functional parameters: swimming, developmental activity, blood pressure and electrocardiographic recordings.

There were no consistent effects of dose on any of the physical or functional parameters evaluated, although caffeine reduced maternal weight gain at all doses evaluated.

The maternal LOAEL is 10 mg/kg bw/day, based on reduced weight gain. The maternal NOAEL is <10 mg/kg bw/day.

The developmental NOAEL is >40 mg/kg bw/day, the highest dose administered.

The developmental toxicity study in the rat is classified acceptable and satisfies the guideline requirement for a developmental toxicity study (OPPTS 870.3700; OECD 414) in rats.

In a further developmental toxicity study (Collins et al., 1983), Caffeine (purity >=98.5%) was administered to 61 Osborne-Mendel rats/dose in water at dose levels of 0, 70, 180, 360, 700, 1000, 1500, or 2000 ppm (0, 10.1, 27.4, 50.7, 86.6, 115.8, 160.9, or 204.5 mg/kg bw/day) from days 0 through 20 of gestation.

Dose levels of 700, 1000, 1500 and 2000 ppm caused significantly lowered total maternal weight gains from day 0 to day 20. Dosages of >=1500 ppm were associated with decreased implantation efficiency, increased resorptions and decreased mean numbers of viable fetuses. Numbers of runts were significantly increased after dosages of >=1000 ppm. Fetal body weight and length were decreased and edematous fetuses were increased at dosages of >= 700 ppm. Caffeine produced no dose-related gross anomalies. Sternebral ossification deficiencies were increased at all dose levels except 70 ppm. Skeletal ossification deficiencies were increased in a dose-related manner at the four highest dose levels.

The maternal NOAEL is ca. 50.7 mg/kg bw/day. (360 ppm in the drinking water).

The developmental NOAEL (embryo-/fetotoxicity is ca. 10.1 mg/kg bw/day (70 ppm in the drinking water), based on delayed ossification.

The developmental NOAEL (teratogenicity) is >204.5 mg/kg bw/day (2000 ppm in the drinking water, the highest dose administered).

The developmental toxicity study in the rat is classified acceptable and satisfies the guideline requirement for a developmental toxicity study (OPPTS 870.3700; OECD 414) in rats.

In a battery of developmental toxicity investigations (Gilbert and colleagues, 1988-1994) Caffeine (USP grade; no further specification) was administered to Cynomolgus monkeys (Macaca fascicularis) in water at dose levels of 0, 150, or 350 ppm from eight weeks before pregnancy to several months after delivery. Several parameters were evaluated: reproductive toxicity, biochemical and physiological examination of the mothers, evaluation of somatic development of the infants, and behavioral tests of the infants.

Exposure to the test substance resulted in a dose-related increase in reproductive failure (stillbirths, miscarriages, decreased maternal weight gain). Analysis of blood and 24-hour urine samples (collected every 2 weeks) revealed a number of both pregnancy and treatment-related effects, namely decreased levels of serum cholesterol and triglyceride during pregnancy in all groups (pregnancy-related); increased levels of serum and urine creatinine in the treated groups (substance-related); unaltered serum glucose level in the high dose group (substance-related, this value usually declines during pregnancy); and depressed levels of serum estrogen in the high dose group (substance-related).

Infant body weights and somatic measurements were reduced over the first 30 days in males, as were a number of initial somatic measurements in male and female infants. The deficits were reversible and not evident after one year of age.

Behavioural tests with the infants indicated that in utero exposure to caffeine and its metabolites resulted in altered behavioural patterns in infant monkeys.

The developmental toxicity studies in the monkey are classified acceptable. Although the investigations do not follow any current test guideline, these results may be helpful for assessment of Caffeine for human use since the study procedure mimics important details of human Caffeine use.

HUMAN DATA

Christian and Brent 2001 concluded in a review on reproductive and developmental risks of caffeine that the usual range of human exposures to caffeine from food and beverages is below the threshold dose that would result in developmental/teratogenic or reproductive effects. Studies evaluating a potential risk on human reproduction can be summarized as follows:

•  With regard to the endpoints low birth weight and spontaneous abortion, some studies of good quality and power have suggested an increased risk with higher coffee consumption (mostly more than 300 mg/day).
• Delayed conception was reported in association with coffee consumption of four to seven cups/day or caffeine consumption as little as 100 mg/day (total dose). However, these findings were not confirmed in other studies or a slight association was only seen in women who smoked and also consumed at least 8 cups of coffee per day. Lack of information on confounder suggests that these findings need further verification.
• It might be suggested that caffeine intake up to 3-4 cups/day or 300 mg caffeine/day is unlikely to cause a relevant reduction in birthweight. However, it cannot be excluded that higher caffeine consumption (>300 mg/day) exerts a small, but measurable effect on fetal growth.
• Information concerning Prematurity was insufficient for conclusions to be drawn about an effect of coffee consumption by IARC, 1991, whereas caffeine consumption over a range of moderate to high intakes has been reported to increase the risk of prematurity in a recent study, caffeine intake up to 3-4 cups/day or 300 mg caffeine/day is unlikely to be causally related to spontaneous abortions. Nevertheless, in some subgroups of women (e.g. non-smokers, women with nausea), higher caffeine consumption (>300 mg/day) might increase the risk of spontaneous abortions.
•  Information on caffeine intake during pregnancy showed developmental delay or central nervous system dysfunction and congenital anomalies with coffee consumption of 2 or more cups of coffee. In conclusion there is no relationship between caffeine consumption up to 2 cups/day and malformations.

In Browne 2006 (Maternal Exposure to Caffeine and Risk of Congenital Anomalies, A Systematic Review, Epidemiology, 17 (3), 324- 331), a systematic review of the influence of maternal caffeine consumption on the risk of congenital anomalies was performed to provide a critical appraisal of epidemiologic evidence.

Conclusions: There was no evidence to support a teratogenic effect of caffeine in humans. Current epidemiologic evidence is not adequate to assess the possibility of a small change in risk of congenital anomalies resulting from maternal caffeine consumption.

Justification for classification or non-classification

There is no need to classify Caffeine for impairment of fertility or teratogenicity according to the Directive 67/548/EC or GHS criteria.

Indeed, there were some alterations observed in reproductive endpoints; however, these changes occurred at doses that already caused systemic toxicity.